Turning to FIG. 25A, such a high-pressure water cleaning system is shown, to include a nozzle holder 71 provided with seven high-pressure water ejecting nozzles 72 arranged to be equi-angularly spaced apart from each other in a circumferential direction thereof. Each nozzle 72 has one nozzle hole 73 at a center thereof. The cleaning system is configured as a set of a cleaning gun (water jet gun) 70 which carries out cleaning by rotating (orbital motion) the nozzle holder 71. FIG. 25B is a view showing a cleaning trajectory of one high-pressure water ejecting nozzle 72. Turning to FIG. 24, a plurality of (e.g., about fifteen) cleaning guns 70 are arranged at equal intervals on a frame member 74 in the longitudinal direction thereof. An object X, such as a glass plate, is moved at a constant speed across the high-pressure water ejected from the cleaning gun 70, i.e., nozzle arrangement. Thus, the object X is cleaned. In FIG. 24, reference numeral 75 denotes a drive device, for example, a servo motor.
The aforementioned cleaning gun 70 for use in the high-pressure water cleaning system has, for instance, a holder provided with a high-pressure water ejecting nozzle at a tip end of a casing. In the high-pressure water cleaning system in which a high-pressure water tube is coupled to the holder, a support shaft is rotatably supported in the interior of the casing, a bearing whose bearing surface is pivotable is mounted to the support shaft and rotatably supports the holder at a base end thereof, and a swash plate is provided between a rear end surface of the holder and the support shaft such that the swash plate is rotatable together with the support shaft and slidably contacts the rear end surface of the holder.
According to this cleaning gun, when the swash plate provided between the rear end surface of the holder and the support shaft is rotated together with the support shaft in the state where the holder provided with the high-pressure water ejecting nozzles is rotatably supported at the base end side thereof by the bearing of the support shaft rotatably mounted in the interior of the casing, the holder sliding along the swash plate moves around to draw a conical shape, under the state where the spin of the holder is restricted by the high-pressure water tube. In this case, the inclination of the holder is absorbed by the pivot operation of the bearing surface. Therefore, a high-pressure water cleaning operation is carried out in such a manner that the high-pressure water ejecting nozzle provided at the tip end of the holder ejects the high-pressure water in a conical shape. Such a system is disclosed in Japanese Patent No. 2705719, the entire disclosure of which is incorporated herein by reference.
As another prior art of the high-pressure water cleaning system, a cleaning system is disclosed in Japanese Laid-Open Patent Application Publication No. 2002-166235, in which a plurality of high-pressure water ejecting nozzle heads each having a plurality of nozzles are provided above a cleaning conveyor to eject high-pressure water to an object which is conveyed by the cleaning conveyor to be transported into a cleaning chamber, and eject the high-pressure water from the nozzles while rotating. In this system, motors are mounted at a location isolated from the cleaning chamber to independently rotate associated high-pressure water ejecting nozzle heads.
However, the above described conventional high-pressure water cleaning systems are unable to achieve desired cleanliness, high-speed, cleaning uniformity, etc., for the reasons stated below.
One drive motor is built into each cleaning gun. Therefore, rotation driving members such as a bearing and a timing belt, namely, dust generating members, are located within a cleaning area in the cleaning system. In the cleaning gun, dust is generated chiefly from a rotation sealing part. This makes it difficult to achieve a cleanliness of about class 10 (US Federal standard 209D) which is required in, for example, a manufacturing line of liquid crystal panels.
The rotational speed of each nozzle holder (high-pressure water ejecting nozzle) is 1500 rpm. As can be seen from shading in FIG. 25B, the movement trajectory of the high-pressure water shows non-uniformity in cleaning strength in the width direction of the cleaning area, (i.e., the longitudinal direction), leaving a non-uniformly cleaned region on the object X. If the cleaning strength, in particular, the strength of the high-pressure water for cleaning is non-uniform, a circuit board mounted on a glass surface in the liquid crystal panel may be damaged. FIG. 25B shows the movement trajectory of the cleaning water ejected from one nozzle. As shown in FIG. 25B, a region of the width of the movement trajectory of the cleaning water in the state where the nozzles partially overlap with each other is cleaned. Since the cleaning system is provided with the plurality of nozzle head units, the cleaning trajectory of the cleaning system is formed by gathering a plurality of cleaning trajectories of the nozzles.
Since it is necessary to build the servo motor or the rotation device into each cleaning gun, a cost cannot be reduced. In addition, building the devices into the cleaning area and piping or wiring operation are time consuming and troublesome.
The system disclosed in the publication No. 2002-166235 is intended to clean construction erection materials such as a scaffold or a scaffold frame and is different from the objects handled by the present invention. In addition, the system is less suited for cleaning which requires high cleanliness mentioned above.